Multi-point touch-sensitive device

ABSTRACT

A touch-sensitive device includes a first conductive layer and a second conductive layer. The first conductive layer has at least a first edge and a second edge. The second edge is substantially parallel to the first edge and there is a voltage drop across the first conductive layer between the first edge and the second edge when a power supply is coupled to the first edge and the second edge. The second conductive layer is separated from the first conductive layer by a spacer layer. The second conductive layer includes multiple electrically isolated conductive regions. When a plurality of the conductive regions are in contact with the first conductive layer simultaneously, each of the plurality of the conductive regions generates an output signal and the magnitude of the output signal depends at least in part upon the conductive region&#39;s position relative to the first and second edges.

RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.200810141739.9, “A Multi-Point Touch-Sensitive Device,” filed on Aug.28, 2008, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of touch-sensitivedisplays, and in particular to a multi-point touch-sensitive device.

BACKGROUND OF THE INVENTION

Today, almost every electronic application provides a user interface forhuman-machine interactions, such as a push button, a keypad, and amouse. Among various user interface related technologies,touch-sensitive displays (also known as “touch screen” or “touch panel”)are becoming more and more popular for being intuitive anduser-friendly. Touch-sensitive displays are widely used in electronicapplications, in particular, portable devices and public systems. As auser interface, a touch-sensitive display detects a user contact withthe display, translates the user contact into an electronic signal, andtransmits the signal to a signal processor. Through signal analysis, thesignal processor determines the location of the user contact on thetouch-sensitive display and performs one or more correspondingoperations in accordance with the location of the user contact.

SUMMARY

One aspect of the invention involves a touch-sensitive device. Thetouch-sensitive device includes a first conductive layer and a secondconductive layer. The first conductive layer has at least a first edgeand a second edge. The second edge is substantially parallel to thefirst edge and there is a voltage drop across the first conductive layerbetween the first edge and the second edge when a power supply iscoupled to the first edge and the second edge. The second conductivelayer is separated from the first conductive layer by a spacer layer.The second conductive layer includes multiple electrically isolatedconductive regions. When a plurality of the conductive regions are incontact with the first conductive layer simultaneously, each of theplurality of the conductive regions generates an output signal and themagnitude of the output signal depends at least in part upon theconductive region's position relative to the first and second edges.

Another aspect of the invention involves a touch-sensitive device. Thetouch-sensitive device includes a first conductive layer and a secondconductive layer. The first conductive layer has one or more pairs ofsubstantially parallel edges. There is a voltage drop across the firstconductive layer between each pair of substantially parallel edges whena power supply is coupled to the pair of substantially parallel edgesand the voltage drop is substantially proportional to a distance betweenthe two edges. The second conductive layer is parallel to the firstconductive layer and separated from the first conductive layer by aspacer layer. The second conductive layer includes multiple electricallyisolated conductive regions. When two of the conductive regions aresimultaneously in contact with the first conductive layer at respectivelocations, each of the two conductive regions generates an output signalfor each respective pair of edges. The ratio between the output signaland the corresponding voltage drop between the two edges within eachpair is substantially proportional to the contact location's distance toone of the two edges.

Another aspect of the invention involves a touch-sensitive device. Thetouch-sensitive device includes a first conductive layer, a voltagesupply, and a second conductive layer. The first conductive layer hastwo sets of electrodes deployed on two substantially parallel edges ofthe first conductive layer. The voltage supply is coupled to the twosets of electrodes to cause a voltage drop across the first conductivelayer between the two sets of electrodes when a power supply is coupledto the two sets of electrodes. The second conductive layer is separatedfrom the first conductive layer by a spacer layer and the secondconductive layer includes multiple electrically isolated conductiveregions. In some embodiments, the conductive regions are configured suchthat, in response to simultaneous external pressures applied to theconductive regions at respective locations, the conductive regionsgenerate multiple respective output signals, one for each conductiveregion, and the ratio between a respective output signal and the voltagedrop is substantially proportional to the corresponding contactlocation's distance to one of the two sets of electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned features and advantages of the invention as well asadditional features and advantages thereof will be more clearlyunderstood hereinafter as a result of a detailed description ofembodiments when taken in conjunction with the drawings.

FIG. 1 is a block diagram illustrative of a voltage divider.

FIG. 2 is a block diagram illustrative of a device having a singletouch-sensitive region and subject to two finger contactssimultaneously.

FIG. 3 is a block diagram illustrative of a device having multipletouch-sensitive regions and subject to six finger contactssimultaneously in accordance with some embodiments.

FIGS. 4A and 4B are block diagrams illustrative of how the multi-touchdevice shown in FIG. 3 is coupled to and controlled by control circuitsin accordance with some embodiments.

FIGS. 5A through 5C are block diagrams illustrative of a touch-sensitivedevice having multiple conductive regions in accordance with someembodiments.

FIG. 6 is a block diagram illustrative of a cross-sectional view of amulti-point touch-sensitive panel having multiple conductive regions inaccordance with some embodiments.

FIG. 7 is a flow chart illustrative of an overview of data flow within amulti-point touch-sensitive system in accordance with some embodiments.

FIG. 8 is a block diagram illustrative of a first multi-pointtouch-sensitive system in accordance with some embodiments.

FIG. 9 is a block diagram illustrative of a second multi-pointtouch-sensitive system in accordance with some embodiments.

FIG. 10 is a flow chart illustrative of how a multi-pointtouch-sensitive system operates in accordance with some embodiments.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. In the following detaileddescription, numerous specific details are set forth in order to providea thorough understanding of the subject matter presented herein. But itwill be apparent to one of ordinary skill in the art that the subjectmatter may be practiced without these specific details. In otherinstances, well-known methods, procedures, components, and circuits havenot been described in detail so as not to unnecessarily obscure aspectsof the embodiments.

Many technologies can be used to make different types of touch panelstargeting at various industrial applications, including surface acousticwave touch panel, infrared touch panel, capacitive touch panel, andresistive touch panel, etc.

A surface acoustic wave touch panel monitors ultrasonic waves that passover the surface of the touch panel. When the panel is touched by afinger, a portion of the wave is absorbed, constituting a touch event onthe touch panel. This change in the ultrasonic waves is detected toestimate the position of the touch event, i.e., the finger contact onthe touch panel.

An infrared (IR) touch panel employs two different methods to capturetouch events. One method detects thermal induced changes of the surfaceresistance of the touch panel. The other method is to deploy on thetouch panel an array of vertical and horizontal IR sensors for detectingthe interruption of a modulated light beam near the surface of the touchscreen.

A capacitive touch panel is a glass panel coated with a conductive andtransparent material such as indium tin oxide (ITO), light emittingpolymer (LEP) or the like that conducts an electrical current across thetouch panel. The touch panel acts as a capacitor with a carefullycontrolled field of stored electrons in both the horizontal and verticalaxes of the touch panel. The human body also acts as an electricaldevice that has stored electrons and therefore also exhibitscapacitance. When the touch panel's “normal” capacitance field (itsreference state) is disturbed by another capacitance field, i.e., auser's finger, electronic circuits located at the corners of the touchpanel detect the resultant “distortion” in the reference capacitancefield as a touch event, which information can be used to estimate thelocation of the touch event on the touch panel.

A resistive touch panel is composed of multiple layers, including twothin electrically conductive layers, i.e., an upper conductive layer anda lower conductive layer that are separated by a thin space. Atoperation, there is a voltage drop and an electrical current through thelower conductive layer when a power supply is applied to the lowerconductive layer. When a user touches the upper conductive layer of theresistive touch panel using, e.g., a finger or a stylus, the twoconductive layers are brought into contact at a certain point. In someembodiments, the upper conductive layer generates a signal correspondingto the voltage level at the contact point. This voltage signal can beused to measure the location of the contact point on the touch panel. Insome other embodiments, a portion of the electrical current flows intothe upper conductive layer through the contact point, causing a changein the electrical current in the lower conductive layer. The amount ofthe electrical current change is detected as a touch event and used forestimating the location of the contact point on the touch panel. Forillustration, a resistive touch panel generating a voltage output signalis described in detail in the present application. But it will be clearto one skilled in the art that the same teaching also applies to aresistive touch panel configured to detect current changes.

The voltage-based resistive touch panel electrically acts as a voltagedivider with an output terminal. FIG. 1 is a block diagram illustrativeof such a voltage divider. The serially-connected resistors Z₁ and Z₂represent the two portions of the lower conductive layer that is dividedby the contact point with the upper conductive layer. If a power supplyV_(in) is applied to the two opposite ends of the two resistors, avoltage signal at the output terminal V_(out) is:

$V_{out} = {\frac{Z_{2}}{Z_{1} + Z_{2}}V_{in}}$

For ease of illustration, resistive touch panels having voltage outputterminals are described in detail in the exemplary embodiments of thepresent application. But it will be apparent to one skilled in the artthat the invention disclosed in this application is by no means limitedto resistive touch panels and the same invention can be implemented inthe touch panels based on other technologies known in the art.

FIG. 2 is a block diagram illustrative of a device having a singletouch-sensitive region and subject to two finger contactssimultaneously.

The resistive touch panel includes at least two parts, a base 100 and acontact film 200. In some embodiments, the base 100 is a panel made ofhard materials (such as glass) that offers the mechanical stabilityrequired by the device and the contact film 200 is made of softmaterials, e.g., poly ethylene terephthalate (PET), which provides theflexible medium through which the two parts can be connected underpressure. In some embodiments, both the top surface of the base 100 andthe bottom surface of the plastic contact film 200 are coated withconductive and transparent materials like ITO or LEP.

The touch panel may have different shapes, regular or irregular,depending on the specific application that uses the touch panel. Forexample, the touch panel shown in FIG. 2 has a rectangular shape withfour edges. Four sets of electrodes 110 are deployed along the fouredges and they are electrically coupled to the conductive layer on thetop surface of the base 100. The contact film 200 has a signal outputterminal 210 coupled to the conductive layer at the bottom surface.

In particular, the conductive layers that are attached to the base 100and the contact film 200, respectively, are separated in space by aspacer layer (not shown in FIG. 2). When there is no pressure applied tothe top surface of the contact film 200, the two conductive layers areelectrically insulated from each other. When an object such as a fingertip presses the contact film 200, the contact film 200 deforms downwardand brings the two conductive layers into contact.

If there is only a single contact point, e.g., the point represented bythe “+” sign, between the two conductive layers, the location of thecontact point on the touch panel can be determined by (i) applying apower supply to the two sets of electrodes on the left and right edgesof the base 100 and measuring an output signal at the terminal 210 and(ii) applying a power supply to the two sets of electrodes at the upperand lower edges of the base 100 and measuring another output signal atthe terminal 210. Each of the two output signals can help to determinethe x-coordinate and y-coordinate of the contact point of the twoconductive layers, which is therefore the location of the contact point.

If there are two or more finger contacts on the touch panelsimultaneously, which have at least two contact points, the touch panelaccording to the configuration shown in FIG. 2 can only generate twooutput signals corresponding to the x-coordinate and y-coordinate of oneestimated contact point. In this case, the estimated location isprobably an estimate of the average of the two or more finger contactpoints on the touch panel. An electronic application that uses the touchpanel as a user interface device can not interpret the user'sinstruction correctly based on the average of the two finger contactpoints if the averaged finger contact point and the two actual fingercontact points correspond to different interface objects on the touchpanel. To avoid this issue, the user has to be very careful not to havetwo finger contacts with the touch panel at the same time. Thisrestriction also prevents the touch panel from supporting applicationsthat may need the multi-touch feature for more sophisticatedhuman-machine interactive operations.

FIG. 3 is a block diagram illustrative of a device having multipletouch-sensitive regions and subject to six finger contactssimultaneously in accordance with some embodiments.

Like the touch panel shown in FIG. 2, the touch panel in FIG. 3 also hasa base 300 and a contact film 400, each coated with a conductive layer.Four sets of electrodes 310 are distributed on the four edges of thebase 300. To support the multi-touch feature, the conductive layer atthe bottom side of the contact film 400 is divided into six electricallyisolated conductive regions 400-1 through 400-6, each conductive regionhaving its own output terminal 410-1 to 410-6. Because the sixconductive regions are electrically insulated from one another, eachconductive region can generate an independent output signal when thereis a finger contact at each of the six conductive regions at the sametime.

As shown in FIG. 3, each of the six conductive regions is subject to afinger touch at the same time. Simultaneously, a power supply V_(in) isapplied to the electrodes at the upper and lower edges of the base 300and there are six voltage signals at the six output terminals, eachsignal originating from a contact point in the corresponding conductiveregion. Next, the power supply V_(in) is removed from the electrodes atthe upper and lower edges of the base 300 and applied to the electrodeson the left and right edges of the base 300, another six voltage signalsat the six output terminals are generated while the six fingers have notbeen lifted off the top surface of the touch panel. As a result, each ofthe six conductive regions is associated with a pair of signalmeasurements, one associated with the left and right edges and the otherone associated with the upper and lower edges of the base 300. Each pairof signal measurements can be used to estimate a contact point within acorresponding conductive region and six simultaneous and unique fingercontact points on the touch panel can be detected.

FIGS. 4A and 4B are block diagrams illustrative of how the multi-touchdevice shown in FIG. 3 is coupled to and controlled by control circuitsin accordance with some embodiments.

The six dashed-line boxes within the base 300 represent the projectionof the six conductive regions of the contact film 400 onto the base 300.Note that there is no overlapping region between any two adjacentconductive regions. Each of the four control circuits 11 through 14 iscoupled to at least one set of electrodes along one edge of the base300. In some embodiments, a control circuit includes multiple switches,each switch controlling the on/off state at a corresponding electrode.When a switch coupled to an electrode is turned on, an electricalcircuit loop including the switch and the electrode is formed. A fingercontact with any of the six conductive regions generates a voltageoutput signal at the corresponding output terminal. In some embodiments,the touch panel is coupled to and controlled by an Application-SpecificIntegrated Circuit (ASIC), such as a touch panel microcontroller,through the four control circuits. In some other embodiments, the fourcontrol circuits are part of the microcontroller. In some otherembodiments, the touch panel is coupled to multiple touch panelmicrocontrollers, each microcontroller being responsible for controllingthe operation of the touch panel in one or more directions.

Referring again to FIG. 4A, to estimate the y-coordinate of a fingercontact point (e.g., P1) within a particular conductive region, a powersupply V_(in) is applied to the two sets of electrodes at the upper andlower opposite edges of the base 300. Depending on how the controlcircuits 11 and 12 operate, the touch panel generates one or more outputsignals at the output terminal associated with the conductive regionhaving the finger contact. In some embodiments, the switches within thetwo control circuits 11 and 12 are configured to switch on and off inaccordance with a predefined scheme to minimize the error caused by thepillow-shape electric field distortion within the conductive layer onthe base 300. For example, the different switches within the controlcircuits 11 and 12 can switch on and off at the same time during thecourse of detecting the finger contact location. In another embodiment,a pair of switches, one within the control circuit 11 and asymmetrically located one within the control circuit 12, is switched onand off one at the same time. By doing so, multiple measurements aregenerated at the same output terminal and an average of the multiplemeasurements is used for estimating the y-coordinate of the fingercontact point. In some embodiments, the averaged measurement isdetermined by weighting the multiple measurements in accordance with thelocations of their corresponding pair of switches along the edges of thebase 300.

Note that there are many schemes known in the art for operating themultiple switches within each control circuit to achieve satisfactorymeasurements. A Chinese patent application entitled “A touch-sensitivestructure and a resistive touch panel using the touch-sensitivestructure,” filed May 6, 2008 (App. No. CN200810096144.6), is hereinincorporated by reference in its entirety. The schemes disclosed thereincan be applied to the touch panels according to some embodiments of thepresent invention.

The electrically isolated conductive regions on the contact film of aresistive multi-point touch-sensitive device can have different shapesand sizes in accordance with the dimension of the entire touch panel aswell as the requirements by the electronic application. For example,each of the six conductive regions in FIG. 4A is a square of the samesize. This configuration may be desired if the application has the sameor similar resolution requirement for estimating the x-coordinate andy-coordinate of a contact point. In some embodiments, each conductiveregion has a rectangular shape of the same or different sizes. In thiscase, the touch panel may have different resolution requirements alongthe x-axis and the y-axis. In some embodiments, a conductive region is aregular or irregular polygon. In some embodiments, the conductive regionis a circle or an ellipse.

FIG. 4B depicts a top view of a touch panel having multiple conductiveregions. The touch panel has the upper and lower conductive layers. Theupper conductive layer is divided into six rectangular conductiveregions 430-1 through 430-6. The lower conductive layer 420 has fourelectrodes 1 through 4 at its four corners. To measure the y-coordinateof a contact point “P7,” the electrodes 1 and 2 are coupled to the anodeof a power supply and the electrodes 3 and 4 are coupled to the cathodeof the power supply. Because the upper conductive layer is brought intocontact with the lower conductive layer 420 at the contact point P7, theoutput terminal of the conductive region 430-4 generates a voltagesignal whose magnitude has a predefined relationship (e.g.,proportional) with the y-coordinate of the contact point. Aftermeasuring the y-coordinate, the electrodes 1 and 3 are coupled to theanode of the power supply and the electrodes 2 and 4 are coupled to thecathode of the power supply. In this case, the output terminal of theconductive region 430-4 generates another voltage signal whose magnitudehas a predefined relationship (e.g., proportional) with the x-coordinateof the contact point. Note that the voltage measurements in the x and ydirections are made within a short time period during which the upperand lower conductive layers are in contact at point P7 and the fingerhas not been lifted off the top surface of the touch panel.

FIGS. 5A through 5C are block diagrams illustrative of a touch-sensitivedevice having multiple conductive regions in accordance with someembodiments. As shown in FIG. 5A, the touch panel 505 has a rectangularshape and its contact film is divided into 20 triangles of the samesize. Each triangle represents a conductive region 510 with its ownoutput terminal. Using the same scheme described above in connectionwith FIGS. 3 and 4 of measuring voltage output signals when a powersupply is applied to opposite edges of the touch panel 505, it ispossible to detect the x-coordinates and y-coordinates of multiplesimultaneous finger contact points at different conductive regions ofthe touch panel 505. Generally, dividing the contact film into manysmall conductive regions can help to improve the multi-point touchpanel's resolution.

FIG. 5B depicts a touch panel 515 having a contact film that includesmultiple conductive regions of different shapes and different sizes.Some of the conductive regions 520 are of “M”-shape while others 530,540 are of triangle-shape, each conductive region having its own outputterminal. Using the same scheme described above in connection with FIGS.3 and 4 of measuring voltage output signals when a power supply isapplied to opposite edges of the touch panel 515, it is possible todetect the x-coordinates and y-coordinates of multiple simultaneousfinger contact points at different conductive regions of the touch panel515. A touch panel with the configuration shown in FIG. 5B is desired ifthe different regions and/or different directions on the touch panel aredesigned for different uses and therefore have different resolutionrequirements. For example, the touch panel 515 shown in FIG. 5B may havea higher resolution requirement on the edges and in the lateraldirection of the touch panel than the resolution requirement in thecentral region and the vertical direction.

FIG. 5C depicts a hexagon-shape touch panel 525 having multipleconductive regions. The contact film of the touch panel 525 is dividedinto six conductive regions 550, each region being of an equilateraltriangle and having its own output terminal. In this embodiment, assumethat there is a finger contact point “P” with a particular conductiveregion. To determine the location of the finger contact point, a powersupply is applied to the touch panel 525 along three differentdirections, i.e., X-X′ direction, Y-Y′ direction, and Z-Z′ direction.For each direction, there is a separate output signal at the outputterminal 560. This output signal can determine the contact point in thisparticular location. Repeating the same procedure in the threedirections generates three estimates of the contact point's location.Because the relationship between the three directions is known, any twoof the three estimates can be used to uniquely determine the contactpoint on the touch panel and the third estimate can be used to improvethe accuracy of the contact point's location on the touch panel 525. Itwill be apparent to one skilled in the art to perform more measurementsalong other directions if a further improvement of the touch panel'sresolution is desired.

FIG. 6 is a block diagram illustrative of a cross-sectional view of amulti-point touch-sensitive panel having multiple conductive regions inaccordance with some embodiments. Note that the dimensions of the layersshown in the figure are for illustrative purpose only and they do notnecessarily represent the actual dimensions of different layers.

The conductive layer 670 represents a layer coated with conductive andtransparent materials like ITO or LEP on the top surface of the basesubstrate of the touch panel. A spacer layer 660 is deposited on theconductive layer 670. In some embodiments, the spacer layer 660 iscomprised of a two-dimensional array of microdot spacers. The array ofmicrodot spacers separates the upper conductive layer from the lowerconductive layer to avoid accidental or unintended contacts. In someembodiments, the array of microdot spacers is printed onto the lowerconductive layer 670 by a proprietary process that has precise controlover dot size, height and density. In some embodiments, a predefined dotdensity determines the corresponding operation method supported by thetouch panel. For example, a low dot density may be sufficient for fingercontacts with a large fingerprint. In contrast, a much higher dotdensity may be required to support a stylus-like input device. In someembodiments, there is a slight positive air pressure in the cavitybetween the layers to prevent the accidental or unintended contacts aswell as dirt and dust from damaging the touch panel.

A lower electrode layer 650 is distributed along the edges of theconductive layer 670. The electrode layer 650 and the conductive layer670 are electrically coupled together. In some embodiments, the lowerelectrode layer 650 is comprised of two or more electrically insulatedportions and each portion is electrically coupled to a set of electrodesdeployed along the same edge of the base 300 as shown in FIG. 3. Whenthe anode and cathode of a power supply is connected to the two sets ofelectrodes at the two opposite edges of the conductive layer 670, thereis a current flow through and a voltage drop across the conductive layer670.

The conductive layer 610 represents another layer coated with conductiveand transparent materials like ITO or LEP on the bottom surface of thecontact film of the touch panel. The dashed-lines in the conductivelayer 610 indicate that the layer is divided into multiple electricallyisolated regions 610-1, 610-2, and 610-N. An upper electrode layer 620is deployed along the edges of the conductive layer 610. In someembodiments, this upper electrode layer 620 is divided into multipleelectrically isolated segments and each segment is electrically coupledto one of the conductive regions 610-1, 610-2, and 610-N in the upperconductive layer 610. When a conductive region of the upper conductivelayer 610 is brought into contact with the lower conductive layer 670 ata particular point, a voltage signal is transmitted through a segment ofthe upper electrode layer 620 to a corresponding output terminal andthen to a microcontroller coupled to the touch panel.

Two electrically insulators 630 are each attached to a respective sideof the upper and lower electrode layers 620 and 650, which are used toprevent the two electrode layers 620 and 650 from being coupled to eachother and avoid potential malfunction of an electronic application usingthe multi-point touch panel. In some embodiments, the two electricallyinsulators 630 are combined together by a double-sided adhesive layer640. In some other embodiments, the double-sided adhesive layer 640itself is an electrically insulator. In this case, the two upper andlower electrode layers 620 and 650 are directly attached to thedouble-sided adhesive layer 640 together and the two electricallyinsulators 630 can be saved.

FIG. 7 is a flow chart illustrative of an overview of data flow within amulti-point touch-sensitive system in accordance with some embodiments.

The multi-point touch-sensitive system includes a screen 710, anapplication microprocessor 720, a touch panel microcontroller 730, and amulti-point touch panel 740 as described above. In some embodiments, themulti-point touch-sensitive system is or is part of a portableelectronic application such as a mobile phone, a game console, a globalposition system (GPS), and a personal digital assistant (PDA). In someother embodiments, the multi-point touch-sensitive system is or is partof a public system such as an ATM machine at a bank's branch office, anautomatic ticket seller at a train station, and a book circulationregistration system in a public library. In some other embodiments, themulti-point touch-sensitive system is or is part of an automobileelectronic control system or a product manufacturing control system.

At operation, the microcontroller 730 sends instructions to the touchpanel 740 through the control signal 19 to detect user-entered commandsor requests using multiple finger contacts or a multi-contact pen-liketool simultaneously. Upon receipt of the user requests, the touch panel740 generates multiple output signals 20 from the multiple conductiveregions as described above and transmits the output signals 20 to themicrocontroller 730. The microcontroller 730 processes the outputsignals 20 to determine the location-related information 17 of themultiple contacts and sends the location-related information 17 to theapplication microprocessor 720 (e.g., a CPU processor).

The microprocessor 720 performs predefined operations based on thelocation-related information 17 and displays operation results 16 on thescreen 710. For example, the user may use a multi-point finger gestureto rotate a picture displayed on the screen. Based on the multiplefingers′ movement on the screen, the microprocessor 720 replaces theoriginal picture with a rotated picture by rotating the picture by,e.g., 90°. In some embodiments, the microprocessor 720 also sends replysignals 18 back to the microcontroller 730. Based on the reply signals18, the microcontroller 730 may issue new instructions to the touchpanel 740. In some embodiments, the microprocessor 720 and themicrocontroller 730 correspond to different circuitry regions within oneintegrated circuit such as an ASIC.

FIG. 8 is a block diagram illustrative of a first multi-pointtouch-sensitive system in accordance with some embodiments.

There are multiple communication channels between the touch panel 810and the touch panel driver 820. For illustrative purpose, assume thatthe touch panel 810 has the same structure as the one shown in FIG. 3.The output terminals V_(in1) through V_(in6) are each coupled to one ofthe six conductive regions in the upper conductive layer and areconfigured to generate and export voltage signals when there aremultiple simultaneous finger contacts with the top surface of the touchpanel 810.

Upon detecting an output signal from any of the six conductive regions,the touch panel driver 820 notifies the microcontroller 830 using aninterrupt signal 827. The microcontroller 830, in response, sendsoperation instructions 825 to the touch panel driver 820, the operationinstructions including measuring the voltage outputs at the sixconductive regions and translating the outputs, if any, into thecoordinates of a touch event at a corresponding conductive region. Insome embodiments, the touch panel driver 820 includes multiple voltagesignal measurement units, each unit responsible for monitoring one ormore conductive regions. These multiple voltage signal measurement unitsmay work in parallel. In some other embodiments, the touch panel driver820 includes a single signal measurement unit. In this case, the unit isresponsible for monitoring all the conductive regions on the touch panelin a sequential manner, one region at a time. In some embodiments, thetouch panel driver 820 and the microcontroller 830 have a sufficientlyhigh signal processing capacity. Thus, the multi-point touch-sensitivesystem is able to detect whether there is a touch event in any of themultiple conductive regions, and if there is a touch event at aparticular conductive region, estimate the corresponding location of thetouch event. Although the touch events at different conductive regionsare determined sequentially, they are virtually simultaneous from theuser's perspective. Whether the touch panel driver 820 includes one ormultiple signal measurement units depends on the specific applicationthat employs the multi-point touch panel.

After determining the locations of the multiple, simultaneous orvirtually simultaneous touch events, the microcontroller 830 performsoperations on the objects displayed on the screen 840 that areidentified by the locations. For example, if the user applies amulti-point finger gesture to rotate a picture displayed on the screen840, the microcontroller 830 replaces the original picture with arotated picture by rotating the picture by, e.g., 90°.

FIG. 9 is a block diagram illustrative of a second multi-pointtouch-sensitive system in accordance with some embodiments.

The multi-touch input panel 910 is coupled to a microcontroller 920. Insome embodiments, the microcontroller 920 is an ASIC chip includingmultiple circuits. In some other embodiments, the microcontroller 920 isan electronic system that is comprised of multiple ICs, each IC having aspecific function. For example, the panel drive 930 is responsible forcontrolling the switches, e.g., turning on/off the switches, in thedifferent control circuits shown in FIG. 4A. By scheduling the on/offsequence of the switches in different directions, the multi-pointtouch-sensitive system can measure the x-coordinates and y-coordinatesof the respective touch events, simultaneous or not, at differentconductive regions.

The multi-touch panel 910 submits its output signals from differentconductive regions to a noise filter 940. Many noise suppressionalgorithms known in the art can be implemented in the noise filter 940to improve the output signals' resolution and reduce the error ofestimating the locations of the touch events. After suppressing noise inthe output signals, the noise filter 940 passes the output signals tothe A/D converter 950 in the control section circuit 960. The A/Dconverter 950 digitizes the analog output signals generated by the touchpanel 910. The resolution of the A/D converter 950, to some extent,affects the resolution of the multi-touch panel 910. A typical A/Dconverter in a multi-point touch-sensitive system has at least 8 bits,and maybe 12 bits or more.

The control section circuit 960 includes or is coupled to an erasablememory device 970. In some embodiments, the memory device 970 stores oneor more signal processing algorithms for estimating the touch eventlocation information based on the digitized output signals. The size ofthe memory device 970 depends on the complexity of the signal processingalgorithms. A typical memory chip has at least 4K bits or more. Thecontrol section circuit 960 retrieves one or more signal processingalgorithms from the memory device 970 and applies the algorithms to thedigitized output signals generated by the A/D converter 950 to determinethe locations of the corresponding touch events on the multi-touch panel910.

In some embodiments, the microcontroller 920 includes one or moreinterface circuits 980. Through the interface circuits 980, themicrocontroller 920 is coupled to other devices within the sameelectronic application (e.g., the microprocessor 720 in FIG. 7) or someother electronic applications external to the multi-pointtouch-sensitive system. Information about the touch events can betransmitted to the other devices or applications through the interfacecircuits 980. The other devices or applications can also sendinstructions to the multi-point touch-sensitive system through theinterface circuits 980. In some embodiments, the interface circuits 980are proprietary devices designed for a specific application. In someother embodiments, the interface circuits 980 are interface circuitsthat are compatible with standard I/O protocols, such as USB and RS-232.

FIG. 10 is a flow chart illustrative of how a multi-pointtouch-sensitive system operates in accordance with some embodiments. Asdescribed above in connection with FIGS. 7 through 9, a multi-touchdetection system typically includes a touch-sensitive device, amicrocontroller coupled to the touch sensitive device, and an electronicapplication coupled to the microcontroller. The touch-sensitive devicehas multiple electrically isolated conductive regions that areconfigured to detect simultaneous finger contacts with thetouch-sensitive device.

In response to detecting multiple simultaneous contacts a user has withthe conductive regions (1010), the touch-sensitive device generatesmultiple output signals (1020). In some embodiments, there is one signalfor each of the multiple simultaneous contacts. In some embodiments, themultiple output signals are generated simultaneously. In some otherembodiments, the multiple output signals are generated sequentially. Insome other embodiments, the multiple output signals are divided intomultiple sets. While the output signals within a particular set aregenerated sequentially, the output signals from different sets aregenerated simultaneously.

The multiple output signals are transmitted to the microcontroller(1030). In some embodiments, the microcontroller includes multiplesignal processing units, each unit responsible for processing one ormore output signals. The multiple signal processing units process themultiple output signals in parallel. In some other embodiments, themicrocontroller has one signal processing unit that processes themultiple output signals sequentially, one signal at a time. In someother embodiments, the microcontroller prioritizes the output signals inaccordance with their associated conductive regions. For example, anoutput signal associate with a conductive region at a particular regionof the touch panel (e.g., the central region) is given a higherpriority. Accordingly, the microcontroller processes this output signalfirst before processing another output signal associated with anotherconductive region (e.g., near the edge of the touch panel). In someembodiments, this feature of ranking or prioritizing the conductiveregions takes into account of the different sizes of the conductiveregions. For example, an output signal from a large conductive region isprocessed before an output signal from a small conductive region. Insome embodiments, this feature of ranking or prioritizing the conductiveregions is required by an electronic application that uses themulti-point touch-sensitive system. For example, a computer game consoleor an ATM machine may perform one operation associated with one objecton the touch screen in response to a user selection of the objectthrough one finger contact only if there is a simultaneous or previoususer selection of another object on the touch screen through anotherfinger contact. In other words, an inherent sequence of user interactingwith different objects on the touch screen may require a processingorder of the user's simultaneous finger contacts with the objects. Insome embodiments, the multiple conductive regions on the multi-touchpanel are prioritized differently over time for different applicationssupported by the touch-sensitive system. In some other embodiments, thispriority change is user-configurable.

The microcontroller is configured to generate one or more controlsignals in response to the output signals and transmit the controlsignals to the electronic application (1040). The electronic applicationincludes a screen displaying multiple human-machine interactive objects.Exemplary human-machine interactive objects include text, virtual pushbutton, images, and virtual keypad. In response to the control signals,the electronic application alters the appearance of the human-machineinteractive objects on the screen (1050). For example, the electronicapplication may rotate an image or highlight a user-selected region onthe screen.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

1. A touch-sensitive device, comprising: a first conductive layer having at least a first edge and a second edge, wherein the second edge is substantially parallel to the first edge and there is a voltage drop across the first conductive layer between the first edge and the second edge when a power supply is coupled to the first edge and the second edge; and a second conductive layer separated from the first conductive layer by a spacer layer, wherein the second conductive layer includes multiple electrically isolated conductive regions; wherein, when a plurality of the conductive regions are in contact with the first conductive layer simultaneously, each of the plurality of the conductive regions generates an output signal and the magnitude of the output signal depends at least in part upon the conductive region's position relative to the first and second edges.
 2. The device of claim 1, wherein the multiple electrically isolated conductive regions are of one size.
 3. The device of claim 1, wherein the multiple electrically isolated conductive regions are of at least two sizes.
 4. The device of claim 1, wherein at least one of the multiple electrically isolated conductive regions has a shape of a polygon.
 5. The device of claim 4, wherein the polygon has a regular shape.
 6. The device of claim 4, wherein the polygon has an irregular shape.
 7. The device of claim 4, wherein the polygon has a shape selected from the group consisting of circle, ellipse, triangle, rectangle, square, and hexagon.
 8. The device of claim 1, wherein at least one of the first and second conductive layers is made of a conductive and transparent material.
 9. The device of claim 8, wherein the conductive and transparent material is indium tin oxide.
 10. The device of claim 8, wherein the conductive and transparent material is light-emitting polymer.
 11. The device of claim 1, further comprising: a first plurality of electrodes deployed at the first edge of the first conductive layer; and a second plurality of electrodes deployed at the second edge of the first conductive layer.
 12. The device of claim 1, further comprising: multiple output terminals, wherein each output terminal is coupled to one of the multiple electrically isolated conductive regions.
 13. The device of claim 1, further comprising: an electrically insulating layer having a first side and a second side opposite the first side, wherein the electrically insulating layer is attached to the first conductive layer at the first side and to the second conductive layer at the second side.
 14. The device of claim 1, wherein the first conductive layer has a third edge and a fourth edge, wherein the third edge is substantially parallel to the fourth edge and there is a voltage drop across the first conductive layer between the third edge and the fourth edge when a power supply is coupled to the third edge and the fourth edge; and when a plurality of the conductive regions are in contact with the first conductive layer simultaneously, each of the plurality of the conductive regions generates an output signal and the magnitude of the output signal depends at least in part upon the conductive region's position relative to the third and fourth edges.
 15. The device of claim 14, wherein the third edge is substantially orthogonal to the first edge.
 16. A touch-sensitive device, comprising: a first conductive layer having one or more pairs of substantially parallel edges, wherein there is a voltage drop across the first conductive layer between each pair of substantially parallel edges when a power supply is coupled to the pair of substantially parallel edges and the voltage drop is substantially proportional to a distance between the two edges; and a second conductive layer parallel to the first conductive layer and separated from the first conductive layer by a spacer layer, wherein the second conductive layer includes multiple electrically isolated conductive regions; wherein, when first and second of the conductive regions are simultaneously in contact with the first conductive layer at respective first and second locations, each of the first and second conductive regions generates an output signal for each respective pair of edges, and the ratio between the output signal and the corresponding voltage drop between the two edges is substantially proportional to the contact location's distance to one of the two edges.
 17. The device of claim 16, further comprising: a first plurality of electrodes deployed at the one edge of each pair of substantially parallel edges; and a second plurality of electrodes deployed at the opposite edge of the pair of substantially parallel edges.
 18. The device of claim 16, further comprising: multiple output terminals, wherein each output terminal is coupled to one of the multiple electrically isolated conductive regions.
 19. A touch-sensitive device, comprising: a first conductive layer having first and second sets of electrodes deployed on two substantially parallel edges of the first conductive layer; a voltage supply coupled to the first and second sets of electrodes to cause a voltage drop across the first conductive layer from the first set of electrodes to the second sets of electrodes when a power supply is coupled to the first set of electrodes and the second sets of electrodes; and a second conductive layer separated from the first conductive layer by a spacer layer, wherein the second conductive layer includes multiple electrically isolated conductive regions; wherein the conductive regions are configured such that, in response to simultaneous external pressures applied to a plurality of the conductive regions at respective locations, the plurality of conductive regions generate respective output signals, and the ratio between a respective output signal and the voltage drop is substantially proportional to the corresponding contact location's distance to one of the two sets of electrodes.
 20. The device of claim 19, further comprising: an electrically insulating layer having a first side and a second side opposite the first side, wherein the electrically insulating layer is attached to the first conductive layer at the first side and to the second conductive layer at the second side. 